Patent GB-487145-A (GB)
Title: Improvements in and relating to automatic steering systems for dirigible craft
IPC: G05D1/08
Filed: 1936-09-12
Abstract: 487,145. Ships' steering-gear. BRETTELL, F. G. (Holmes, R. V.) Sept. 12, 1936, No. 24918. [Class 114] [Also in Group XXXV] An automatic steering system comprises a rudder motor, a direction-responsive instrument, a controller worked from the instrument which causes actuation of the rudder motor for predetermined fixed time intervals and means for keeping the controller and rudder in register, for instance on the completion of each return movement of the rudder without the inclusion of a follow-up connection. The rudder is actuated, as by including a variable resistance in the motor, to have a tendency to unequal movements toward and away from the neutral position. The apparatus may be set to provide a " virtual " mean helm for weather conditions, or may be adjusted to seek such automatically. The system also provides for hand steering and for remote non-automatic control of the rudder motor. The coupling of the controller with the compass is effected magnetically by an arrangement such as is described in Specification 346,272. The steering system includes a tiller 31, Fig. 1, clamped to the rudder stock, a quadrant Q free thereon but in geared connection with an electric motor M carried by the quadrant. Hand steering is effected by cables 18 connecting the quadrant with a hand wheel W, the motor then being stationary so that the quadrant and tiller are locked and move together. When the quadrant is held fixed as by a stop 19, the tiller moves relative thereto when the motor M is energized in accordance with a control unit C which itself moves in response to motion of the compass 21 when the ship moves off its course. The unit C is connected by wiring 24, with the motor M, by wiring 25 with a battery S and by wiring 22 with the compass contacts. Instead of acting directly on the motor, the control may act upon the valve of a steam steering engine. The tiller 31 carries a shaft which is geared to the rudder stock and which supports a disk 51 with conducting segments which co-operate with brushes to act as limit switches to stop the motor M when the quadrant reaches its outer limits of motion, and when in its neutral positions 57. The disc may be adjusted so that the neutral position is not precisely set for the rudder in a fore and aft position. The arm 146 of a main switch 108 can be placed in four positions, one for cutting out the whole system, one for bringing all parts to neutral prior to hand steering, one R for use when a remote control is required and one C when automatic control by the compass is required. With the switch in position C a constantly running motor 64 drives a pinion 68 having segments 69 which co-operate with the brush 71 and energizes the solenoid 115 for timed periods whereby the contact arm 114 is raised to the compass contacts. When the ship is on its course, the arm 114 remains in alignment with the zero contacts and no current flows to the rudder motor. When the ship is off its course the arm 114 engages a contact such as 1L whereupon the magnet 95 is energized and the arm 79 is swung to bring pinions 77 and 78 into engagement whereby the shaft 81 is rotated. The same movement of arm 79 raises the contact arms 143, 144, 145 to close two circuits. One circuit includes a segmental disc 88 on the shaft 87 which is driven from shaft 81 and maintains the solenoid 115 energized even when the timer 68 breaks its circuit. The disc circuit is broken six times per revolution thereof in staggered relation to the solenoid circuit breaker so that magnet 95 remains energized until the controller 119, on the shaft 81 moves to the position when an insulating segment coincides with the corresponding controller brush C1L, the steering motor then moves the rudder to the left, the circuit comprising positive terminal of S, fuse F, switch arm 146, contact C, wires 165, 166, relay arm 105, relay contact 167, motor variable resistance 109, wire 168, switch arm 144, contact 169, wire 171, limit switch contacts 172, 173, conducting segment 51, field winding WL and armature 174 of motor M, wire 175, contact 176, arm 106 of relay 104 back to earth. The relay 104 is connected with a disc 137, also carried by the shaft 81, and has an insulating segment 139 whereby the rudder on its return swing is stopped in its central position, by interruption of the motor circuit, even when the controller has not reached its central setting. As long as contact arm 114 contacts with compass point 1L, the rudder is maintained in the position to which it has been moved as the steering motor and magnet are de-energized by coincidence of insulating segment 122 of controller disc 118 and brush CIL which results in the arm 79 returning to neutral position and raising of contacts 143, 144, 145 to break the steering motor circuit at 169. The connections are such that the resistance 109 is not in circuit when the rudder is being returned to its central position so that the motor then runs faster than when putting on rudder. When the craft swings so that an outer contact as 3L is engaged by the arm 114 the rudder is moved to the left as before, but when as the ship swings back on its course the arm 114 contacts with 2L the connections are then such that the rudder is moved to the right. On rapid and large swings corresponding to co-action of arm 114 with 4L the motor swings the rudder to the limit position and is held by breaking the circuit through the limit switch until the ship swings back to a position corresponding to 3L when the connections are remade to reverse the motor through a change-over switch which is constituted by an insulating sector 124 which is frictionally engaged with disc 118 and has an arm 136 positioned between stops 134, 135. As the disc 118 reverses the sector is moved from one end position to the other and the segments 125, 126 thereof co-operate with brushes 127, COR2, COR3 and 131, COL2, COL3 respectively to reverse the motor circuits. For cutting out the automatic control and providing hand control of the rudder motor a second switch 201 is connected to the main switch 108 and to a hand control within a flexible rubber tube 206. When the tube 206 is pressed at COM the switch X throws the compass control in by connecting terminals 154 and 202. When pressed at REM, switch X is thrown over to the opposite position to complete the remote control circuit. With the bar 207 of switch K neutral the rudder is in mid position, whilst with pressure at LE or R1 respectively contact is made with 215 or 214 to cause the rudder motor to move to the left or right. When two rudders are to be actuated, the quadrant drives a shaft carrying a transverse arm the ends of which are pivotally connected to tillers on the rudders. For larger craft the centring device on the tiller is omitted and the virtual mean helm is obtained automatically by arranging for the motor to run faster when putting on helm than when taking it off.